Electric condenser



Jan. 1, 1952 H. F. scHwARz ETAL ELECTRIC CONDENSER Original Filed Aug. 27, 19.45

,Pnenad Jan. 1, 1952 ELECTRIC CONDENSEB Harvey Fisher Schwarz and William Joseph OBrien, London, England, assignors to The Decca Record Company, Limited, London, England, a corporation of Great Britain Original application August 27, 1945, Serial No. 613,004. Divided and this application April 5, 1950, Serial No. 163,582. In Great Britain Feb`- mary 29, 1944 Section 1, Public Law 690, August 8, 1946 Patent expires February 29, 1964 l Claim. l

This invention relates to electric condensers, and particularly those of the silvered mica type. and has for an object to provide a condenser having a high degree of stability in respect of capacity. One of the factors which affects the stability of a condenser is variation in humidity conditions of the atmosphere and one of the common ways of rendering small condensers immune to such changes, is hermetically to encase them in wax, or the like, after the outer metal surfaces have been covered by layers of material having good insulating properties. Unless these layers, however, adhere securely to the metal surfaces, there is a danger of the encasing wax creeping between them and the metal, thereby altering the capacity of the condenser, due to the presence of high di-electric material at the metal edges. Furthermore, the stability is affected by the unstable electrical properties of the wax, such as its unstable temperature coeilicient. Furthermore, the attachment of the conductors to the plates of the condenser also renders 1t diiiicult to maintain the close adherence of the outer layers to the metal surfaces, and also presents certain other manufacturing difliculties.

This application is a division of a copending application filed by Harvey Fisher Schwarz and William Joseph OBrien, Serial No. 613,004, filed August 27, 1945, and entitled Electric Condensers. now abandoned.

According to the present invention, an electric condenser comprises a two-part casing of comparatively rigid insulating material in which are housed condenser plates comprising outer layers of metal separated by di-electric, each of which housing parts is provided with a metal contact adapted to engage respectively the outer layers of metal, at least one of which contacts is resiliently mounted on its partl of the casing, means for clamping said parts of the casing together, and means for attaching leads to said contacts. It will be appreciated that this arrangement eliminates the necessity of encasing the condenser plates in wax, and the possibility of the wax creeping between the plates. Furtherm'bre, it eliminates the diillculty of attaching the leads to the metal layers.

2 the iiat abutment face to accommodate itself to the metal layer under the action of said resilient means. For example. each contact may be formed from pliable metal sheet, shaped to provide an arm which at one end is attached to the casing part, and the other end of which provides the aforesaid abutment face. The abutment face may be maintained in contact with the metal layer, either by reason of the resilience of the arm or by reason of an additional resilient member disposed between the abutment face and the part of the casing. In one construction, the aforesaid contact may be shaped in the form of a question-mark, one end of which is secured to the casing part as by a rivet, and the other end is provided with a flat abutment face comprising a disc formed integrally with the curved Preferably, the metal contacts are arranged y part of the arm, but severed therefrom, except for a short neck. In order to stifen the disc, it may be embossed. The leads for the contacts are secured on the outside of the casing by the same rivets which attach the contacts to the casing.

The aforesaid two-part casing may be rectangular or circular in configuration, a spigot connection being provided'between the two parts. The casing parts may be moulded from a plastic.

Each part of the casing may be provided with an upstanding boss or projection opposite the fiat abutment face of the contact. One or each of said bosses may be provided with a small helical spring for engaging the at abutment face.

The following is a description of one embodiment of the invention, reference being made to the accompanying drawings, in which:

Figure 1 is a plan view of the condenser casing showing certain parts dotted;

Figure 2 is a side elevation of the arrangement shown in Figure 1;

Figure 3 is a section on the line 3 3 of Figure 1, and

Figure 4 is a plan view of one oi' the contacts.

As will be seen from Figure 2, the condenser casing is formed in two parts I Il and I I, each having the same peripheral contour and provided with lugs I2 having holes I3 therein for receiving tubular rivets I4, as shown in Figures 1 and 2. A spigot joint is provided between the two parts of the casing by means of an upstanding ridge I5 in the part Il engaging a recess I6 in the Dart I0. The part II is provided with a central solid boss I1 while the part I0 is provided with a somewhat longer boss I8 having a central bore I9 therein.

The lengths of the two bosses are such asto provide a sumcient gap between them for accommodating two contacts arranged one on either side of a rectangular condenser plate 2|. The condenser plate is of such a size as to leave a small gap between its edges and the walls of the casing. The condenser plate may be formed in the manner described in co-pending United States patent application No. 613,003, now abandoned, by spraying metal on to the opposite sides of a sheet of di-electric which is masked so as to leave a marginal portion 22 uncovered. Each contact may be stamped from thin pliable metal sheet so as to have a shape as shown in Figure 4. As will be seen, it comprises an arm 23 somewhat in the shape of a query mark, having at one end a small circular plate 24 perforated at 25 for receiving a rivet 26 by which it is attached to the inside of one oi' the casing parts, which rivet is also employed for connecting a lead to the contacts from the outside of the casing. The other end of the arm 23 is connected by a narrow neck 28 to a disc which is embossed to provide a flat central portion 29 from which extends a conical flange portion 30, which provides the disc with the required amount of rigidity. The flat portion of each embossed disc is arranged over one or other of the bosses I1 or I8 on the casing parts. The hollow boss I8 is provided with a small compression spring 30a which engages one of the contacts and presses it, together with the condenser plate, against the other contacts and against the solid boss I1. After the parts have been assembled in the above manner, the assemblage may be encased inwax.

Instead of the two-part casing being enveloped.

in wax the two edges o1' the parts of the casing before assemblage may be coated with a suitable sealing material or adhesive so as hermetically to-seal the joints.

In order still further to enhance the stability of the condenser the interior of the two-part casing may be supplied with an inert atmosphere, such as nitrogen. For this Purpose, one of the casing parts may be provided with a small aperture, or leakage between co-operating edges of the two casing parts may be utilised, and after `the aforesaid parts have been assembled, they are placed in a chamber, which is first evacuated and then supplied with nitrogen, after which, means may be provided for closing the aperture while one of said electrodes, the lateral extent of said contact means in the plane of said electrodes being less than that of said electrodes, a casing of relatively rigid insulating material defining an interior cavity for containing said unit, the dimensions of said cavity exceeding the dimensions of said unit to leave a free space all around said unit, and means securing said arms of said contact means to said casing on opposite sides of said cavity for supporting said condenser unit between said abutment faces in a position extending said condenser unit between and beyond said lateral extent of said contact means, whereby said condenser unit provides a capacity shield between said contact means to provide a housed condenser having a capacity which does not exceed the capacity of said condenser unit by more than V2 mmfd.

HARVEY FISHER SCHWARZ.

WILLIAM JOSEPH OBRIEN.

REFERENCES CITED lThe following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 1,899,540 Towne Feb. 28, 1933 2,078,284 Schrader Apr. 27. 1937 2,303,391 Rosenthal Dec. 1. 1942 2,304,764 McAllister Dec. 8, 1942 FOREIGN PATENTS Number Country Date '518,127 Great Britain Feb. 19, 1940 

